Method for gasifying coal



1955 E. s. PETTYJOHN ET AL 2,715,573

METHOD FOR GASIFYING COAL Filed May 27, 1950 2 Sheets-Sheet l jams/22,273

1955 E. s. PETTYJOHN ETAL 2,715,573

METHOD FOR GASIFYING CQAL 2 Sheets-Sheet 2 Filed May 27, 1950 UnitedStates Patent Ofiice 2,715,573 Patented Aug. 16, 1955 2,715,573 IVIETHODFOR GASIFYING COAL Application May 27, 1950, Serial No. 164,692 6Claims. (Cl. 48206) This invention relates to a method and apparatus forpreparation of calorific gases by the gasification of finely subdividedcoal suspended in a flowing gas.

An object of this invention is to provide method and apparatus of thenature indicated capable of efiiciently utilizing coal of high ashcontent to gasify such coal continuously and with a high output ofcalorific make gas per unit of apparatus space.

Other and further objects and features of the present invention willbecome apparent from the following description and appended companyingdrawings showing, diagrammatically and by way of examples, apparatusaccording to the present invention. More particularly:

Figure l is a side View of an apparatus according to the presentinvention;

Figure 2 is another side Figure 1;

Figure 3 is a plan view of the apparatus of Figure 1;

Figure 4 is a fragmentary view similar to Figure 2 but showing amodification of the apparatus of Figures 1 to 3;

Figure 5 is a view similar to Figure 1 but showing still anothermodification of the apparatus of Figures 1 to 3;

Figure 6 is a side elevation, with parts shown in vertical section alongthe line 6-6 of Figure 7, and showing another apparatus according to thepresent invention; and

Figure 7 is a sectional 77 of Figure 6.

When proceeding according to the present invention, finely subdividedcoal is suspended in flowing oxygen enriched air. Combustion of the coalis brought about and a temperature is maintained at which the ashcontent of the coal is slagged and at which carbon monoxide rather thancarbon dioxide is generated. The temperature may be raised to a pointwhere steam may be added to the suspension for bringing about a blue gasreaction.

From a practical operating standpoint, the characteristics in terms ofwhich such a process may be evaluated including the following:

1. Calorific value of make gas 2. Completeness of coal gasification 3.Completeness of recovery of heat content of coal (thermal efl'iciency)4. Amount of gas generated per unit of apparatus space 5. Ease andcompleteness of ash separation 6. Minimum wear and erosion of apparatusItems 1, 5 and 6 are believed to be self-explanatory. By the termcompleteness of coal gasification is meant simply the extent to whichthe coal is gasified or conversely the amount of coal still left inunburned form after passing through the gasification apparatus, nodistinction being made on the basis of the calorific value of the gasproduced. By the term thermal efliciency is meant the amount of heatavailable by combustion of a given amount of make gas cooled to roomtemperature view of the apparatus of view taken along the line claims asillustrated by the acas compared with the heat available by combustionof the amount of coal fed into the apparatus in the manufacture of saidamount of make gas.

From a cost standpoint, it is also important to know the amount of heatrequired (if any) in excess of that derived by combustion of coal beinggasified and the amount of oxygen consumed for enriching the air inwhich the coal is suspended for gasification.

The operating variables which are controlled according to the presentinvention including the following:

1. The ratio of total gaseous oxygen added per unit weight of coal 2.Inlet oxygen concentration of the air-oxygen portion of the gaseoussuspension medium 3. The ratio of steam (if any) to unit weight of coal4. Rate and nature of gas flow through the apparatus 5. Residence timeof gases in apparatus 6. Particle size of coal 7. Temperature ofmaterial entering the apparatus 8. Pressure The above-tabulatedoperating variables, according to the present invention, are adjusted tomaintain, among other things, a temperature high enough to causeslagging of the ash content of the coal and to cause a coal gasificationyielding a maximum amount of carbon monoxide and a minimum amount ofcarbon dioxide. According to specific methods within the scope of thisinvention the temperature is maintained high enough to bring about areaction with added steam.

The fusion temperature of the coal ash depends somewhat on theparticular coal being gasified but generally ranges upwardly from about2200 F. Thus, for practical purposes at least this temperature must bereached and maintained until the slag has been separated from the makegas. Separation of the coal ash from the make gas by slagging is anessential feature of the present invention. However, for other reasons,the operating temperature is in all cases maintained, in at least at onestage in the gasification process, at a temperature in excess of 2200F., as explained hereinbelow. Nevertheless,

even when such a higher temperature is generated and maintained at somestage ahead of the separation of ash, the temperature must not bepermitted to fall to 2200 F. (or to the solidification temperature ofthe ash) until after the ash has been separated.

In the gasification of coal according to the present invention, thecombustion of the coal apparently proceeds in two stages. First, thecarbonaceous material in the coal is oxidized to carbon dioxide and nextthe carbon dioxide is reduced to carbon monoxide by residualcarbonaceous material. At a temperature in excess of 2300 (reduction ofdioxide to monoxide) approaches completion yielding a make gascontaining relatively small amounts of carbon dioxide. Hence, thetemperature is maintained about 2300 F. at least until this second stageof the combustion has been completed.

At temperatures ranging from 2500 to 3000" F., we can add steam, inamounts ranging up to 1 lb. of steam for each pound of coal, to formhydrogen and carbon dioxide by reactions involving steam and carbonmonoxide and steam and carbon.

At temperatures of 3000 F. or higher, we find it possible to carry outboth an incomplete combustion of part of the coal yielding principallycarbon monoxide and a concurrent blue gas reaction with steam and therest of the coal yielding both carbon monoxide and hydrogen.

For maintaining the indicated temperature range, an amount of heat mustbe generated in and/or carried into the gasification chamber equal tothe heat losses occurring at this temperature range. The heat losses inquestion include the heat loss due to radiation and convection; heatlost as sensible heat of make gas; and heat lost due to the more or lessendothermic nature of a gasifying reaction, as when steam is used. Theheat loss due. to radiation and convection. is best indicated in termsof amount of heat lost per unit of coal introduced into the apparatus.The loss of a given amount of heat per unit of time will be more or lesssignificant depending on the amount of coal fed into. the apparatusduringthis unit of time. A

The heat lost as sensible heat of make gas will vary according to the.amount and composition of the make gas produced. For instance, thenitrogen, steam and other non-calorific gas contents of the make. gas.will affect the amount. of heat lost as sensible heat of make gas. 7

The amount of heat generated in. the. gasifying chamber y (when thecarbonaceous material in the coal is burned to carbon monoxide) depends,among other things, upon the completeness of the combustion of this coalor conversely upon how much of this coal passes through the apparatuswithout being burned.

Two of the operating variables controlled for effecting combustion of 'amaximum amount of the coal fed into the gasifying chamber are theparticle size of the coal and the mixing of the coal with the gasesentering the apparatus. We feed the coal into the apparatus in finelysubdivided form. .At least 80% of the coal passes a 100 mesh screen andat least 50% passes a 200 mesh screen. Preferably, practically all thecoal passes through a 100 mesh screen and at least 50% passesthrough a325 mesh screen. This finely subdivided coal is suspended in air oroxygen enriched air and injected tangentially at a rapid rate into acylindrical chamber wherein vertical gas movement is effected.Additionally, oxygen enriched' air or oxygen and, optionally, steam, arealso tangentially injected into the vortex chamber. rapid and completeintermixing of reactants is assured in' the rapidly flowing gaseous coalsuspension. The latter may then be tangentially injected into a secondvortex chamber where combustion and gasification take place. Additionalamounts of air or oxygen enriched air may be injected tangentially intothe. second vortex chamber. Due to the fine particle size of the coaland its intimate intermixture with the suspending gases, the coal isquickly raised to combustion temperature and burned or gasified rapidlyand completely in the second vortex chamber. In other words, the amountof coal passing through the apparatus without being burned is verysmall.

It should be noted, in this connection, that the abovedisclosed fineparticle size of the coal and the intimate. intermixture of the coalwith the reacting gases not only promotes more rapid and completecombustion and gasification of the coal, but also brings abouttheproduction of a make gas having a high ratio of carbon monoxide tocarbon dioxide and therefore characterized by a relatively highcalorific value. 7

Other operating variables that arecontrolled for maintaining the hightemperature include the residence time of the coal suspension and of thegas formed therefrom within the'apparatus and the pressure maintained inthe apparatus. As the weight rate of flow through the apparatus isincreased, thus shortening the residence time, the heat losses perweight unit of coal due to radiation and convection are lessened. Alower limit for the residence time is set by the time required forgasification of the coal with formation of carbon monoxide. Theresidence time is closely correlated with the pressure within theapparatus. Raising the pressure to superatmospheric levels increases theresidence time, for at such increased pressures more weight units of gasare contained. in each space unit of the apparatus, the volume of eachweight unit of gas being inversely proportional. to the pressure.

A temperature of from 2300? to 2500* F. can be maintained by feedingcoal of. the indicated fineness, eifecting intimate coal-gas mixing,

adjusting the residence time Thus,

to about 0.2 to 3.5 seconds and maintaining the apparatus at atmosphericor higher pressure, preferably at from 5 to 7 atmospheres. To raise thetemperature to or above2300 F., and to generate gas efficiently that hasa heating value in excess of 100 B. t. u., the oxygen containing gasmust contain more than 30% free oxygen and may contain as much as- 98%oxygen. An oxygen content of 60% or more is preferred as giving the bestresults. The ratios of total oxygen to coal are disclosed hereinbelow.If a blue gas reaction is to be efiected (at 3000 F. or higher) then thesteam must be preheated at least to 2000 F. and preferably to 2200" F.

While the operating variables must be adjusted to maintain theabove-indicated temperature range, the operating variables may befurther adjusted while maintaining said temperature range to securevarious types of results, as disclosed hereinbelow.

At temperatures below 3000 F. a relatively high ratio of oxygen to coal.favors more. complete coal gasification at the expense of the.calorific. value of the make gas and at the expense of thermal:effi'cien'cy. Conversely, a relatively low ratio of oxygen to coalfavors the formation, of make gas of relatively high calorific valuewithhigh thermal efiiciency, but the coal is gasified less completely. Wehave found further that as the oxygen concentration in the suspendinggas, is increased, the ratios of oxygen tocoal favoring either morecomplete coal gasification or formation of make gas. of relatively highcalorific value with high thermal efficiency are both increased. Somethermal efliciency and calorific value of make gas may be sacrificed tosecure more complete coal gasification, carbon monoxide to hydrogenratio in the make gas can both be lowered by theuse of steam up to about0.5 to 1.0 pound per pound of coal.

At temperatures in excess of 3000 F., and when both steam andoxygen-containing gas are caused to'react with the coal, maximum thermalefficiency, maximum calorific value of make gas and maximum coalgasification may be effected at about the same ratio of oxygen to coal.

In general, the total gaseous oxygen to coal ratio should be maintainedwithin ranges depending on the inlet oxygen concentration and tabulatedas follows:

7 Inletoxygen concentration in percent The above-described methods maybepracticed inapparatus' shown in the. accompanying drawings and describedasfollows:

. In Figures 1 to 3 the reference. numeral 10; indicates generally a.gas-making apparatusconstructed of suitable refractory material. definedagenerally cylindrical-vortex chamber 12 having a horizontal axisa gasenters the vortex chamber 12. through a generally tangential conduit 14.Steam-or other gas is injected into the vortex chamber 12. through asecond generally. from the conduit l4by about Gas is discharged from thevortex chamber 12. dischargeconduit18openingtan- I gentially intoagenerally vertical cylindrical gasification tangential conduit 16;spaced 90 through. a central axial chamber 20-provided near itsbottomwith a slag, outlet 22.and a. gas outlet 24.. The. latter is: arrangedat a slightly higher level. than the slag outlet 22 to' prevent blockingby slag. Additional air or oxygen: enriched air may be.

injected: tangentially into the gasification chamber 20" through. aconduit 26.

In the operation of. the apparatus of- Figures 1 to: 3 a suspensionof:finely divided coal in air;.oxygen enriched air or. oxygen: and-,- ifdesired, some: steam: enters the vortex chamber 12thIouglr the'cond'uit14.-1- The latter is.

and vice versa. The specific gravity and the Within the apparatus. 10;there is:

A. suspension of. finely divided coal in disposed so that the injectedsuspension will have an unobstructed passage until the suspensionimpinges against the steam issuing into the vortex chamber 12 from theconduit 16. The steam thus functions as a protective blanket to preventerosion of the wall of the vortex chamber 12 at the area where otherwisethe coal suspension would impinge directly against the wall of thevortex chamber. The suspension of coal in the two gases injected throughthe conduits 14 and 16 will flow vortically within the chamber 12whereby intimate mixing and se lective grinding of relatively coarsecoal particles will be eflected. The resulting uniformity of particlesize is an advantage for in the subsequent gasification coal particlesof about the same particle size will be gasified more uni formly. Thesuspension of uniformly sized particles in the gaseous mixture passesthrough the conduit 18 tangentially into the gasifying chamber 20 wheregasification takes place, secondary air or oxygen enriched air beingpreferably injected through the conduit 26. The gas flow within thechamber 20 is vortical so that molten slag will collect on the insidewalls and flow down to the bottom of the chamber 20 where accumulatedslag may be removed in molten form through the conduit 22. The make gasis collected through the conduit 24.

In any process where coal particles are raised to a temperature abovethe coking or fusion range, the hot coal particles tend to coke andagglomerate and to be deposited as adherent masses on the walls of theapparatus which interfere with the operation of the apparatus and arediflicult to remove. Further, in any process where a slaggingtemperature is reached, the molten slag tends to accumulate on the wallsof the apparatus, entrapping coal particles and easily forming viscousmasses that may block the apparatus.

In our process the coal particles are very rapidly heated to a coking orfusion temperature, but deposition of the coal particles immediatelyafter injection is prevented by the above-mentioned protective blanketof steam. Past this point the coal particles are suspended and carriedby vortically flowing gas and the volatile content of the coal isvolatilized very rapidly so that the coal is partially devolatilizedbefore again being thrown into contact with a solid surface. When aslagging temperature has been reached in the gasifying chamber 20, theslag will collect on the walls of the apparatus due to the vorticalmovement of a suspending fluid and then flow downwardly to be collectedat the bottom of the chamber 20.

A modification of the apparatus of Figures 1 to 3 is shown in Figure 4when the conduit 14 is constricted as at 15, to form a restricted throator orifice. If an entrainment of coarsely granular coal in a gas iscaused to pass through the conduit 14, the coal granules being smallenough to pass freely through the constriction 15 and if on such passagea pressure drop of at least 15 pounds per square inch is eifected withacceleration of the entraining gas, then the coal granules will beshattered on passing through the constriction 15. Reference is made tothe copending applications of John I. Yellott, Serial Nos. 22,154 and762,589, filed, respectively, April 20, 1948, and July 22, 1947 (nowPatents No. 2,515,542 and No. 2,515,541, respectively), for a detaileddescription of such means and methods for comminution of coal and thelike.

Figure 5 shows apparatus generally similar to that of Figures 1 to 3,except for the fact that the gas flow through the gasifying chambertakes place in an upward direction. As shown, the apparatus of Figure 5generally indicated at and constructed of suitable refractory materialincludes a vortex chamber 32 of cylindrical shape and having an axisextending generally horizontally. A suspension of coal in a gas isinjected tangentially into the vortex chamber 32 through a conduit 34while a blanketing gas is injected tangentially into the vortex chamberthrough a conduit 36. An axial central dis charge aperture 38 affordscommunication between the vortex chamber 32 and the bottom portion ofthe vertical gasifying chamber 40 from which molten slag may bedischarged through a conduit 42 having an inner opening below that ofconduit 38. Additional air or oxygen enriched air may be tangentiallyinjected into the gasifying chamber 40 through a conduit 44. Make gasproduced in the chamber 40 may be collected through a conduit 46.

While the apparatus of Figure 5 functions similarly to that of Figures 1to 3, it may be noted that, since in both gasifying chambers 20 and 40maximum temperature is reached adjacent the discharge openings of theconduits 18 and 38, the maximum temperature in the case of the apparatusof Figures 3 and 5 will be reached immediately above the layer of moltenslag collecting on the bottom of the chamber 40 so that as a result,this slag will be less viscous.

Both the apparatus of Figures 1 and 3 and that of Figure 5 are suitablefor operation at any temperature in excess of 2300 F. Figures 6 and 7,on the other hand, show apparatus especially designed for operation attemperatures of 3000" F. or higher. More particularly, the apparatus ofFigures 6 and 7 includes a heat exchange device for recovering the heatof the make gas produced for utilizing this recovered heat to superheatsteam to 2000 F. or higher.

The apparatus of Figures 6 and 7 includes a cylindrical vortex chamber56 having a vertical axis into which a suspension of coal in air, oxygenenriched air, steam or mixtures thereof is tangentially injected througha conduit 52. Preheated steam at a temperature of 2000 F. or higher isinjected tangentially through a conduit 54. The vortically flowing coalsuspension is discharged centrally and axially from the vortex chamber50 directely into a vertically arranged tubular gasifying chamber 56having, at its bottom, a slag outlet 58 and, provided at a slightlyhigher level, with a hot make gas discharge conduit 60. Additionalpreheated air or oxygen enriched air may be injected into the gasifyingchamber 56 through a conduit 62.

The hot make gas is discharged through conduit 60 into the bottom of afluidizing vessel 64 containing a solid more or less finely subdividedheat exchange medium 66. The hot make gas flows upwardly through thevessel 64 and the heat exchange medium contained therein and passesthrough a gas-solid separator 68 into a discharge conduit 70. The heatedheat exchange medium 66 overflows through a conduit 72 into a steamconduit 74 where the heat exchange medium is picked up by steam to besuperheated (which may contain added air or oxygen enriched air) andcarried by the steam into an upper fluidizing vessel 76. There heatexchange between the steam and the heat exchange medium is completed.The resulting superheated steam passes through a gas-solid separator 18into the conduit 54 while the heat exchange medium flows through aconduit 89 back to the lower fluidizing vessel 64 for reheating byfurther amounts of hot make gas.

The temperature in vortex chamber 50 receiving the coal suspension andsuperheated steam is upwardly of 3000 F. At the slag discharge conduit58, the temperature in the gasifying chamber 56 is at least 2500 F. Thesteam is superheated in the fiuidizing vessel 76 to 2000 F. or higher.

As in the apparatus of Figures 1 to 5, provision is made for aprotective steam lanket to prevent erosion of the apparatus byimpingement of the injected coal suspension. Likewise, intimateadmixture of steam and coal suspension and selective grinding of thecoarser coal particles will be effected in the vortex chamber 56.

In general, the coal suspension is injected into the apparatus ofFigures 1 to 7 at a velocity of at least 150 to 200 feet per second andis thereafter caused to flow through the apparatus at least feet persecond.

We give hereinbelow operating results obtained using U. S. Sieve WeightPercent Passing Results obtained in the apparatus of Figures 1 to 3and'S at atmospheric pressure and at a steam tempera ture not in excessof 900 F. are tabulated as follows:

Lb Percent Exp. Ste/aim] Lb. 02/ Percent 0a] Thermal B. t. 11,, No LbvCoal Lb. Goal 0; Cone. Gasified V Efi. Cu. Ft.

In the apparatus of Figures 6 and 7 at a steam temperature of about 2200F., at an oxygen to coal ratio of about 32% and with the use of 0.6pound of steam perpoundof coal, the following results were obtained. Atan oxygen concentration of 91% of the coal was gasified with a thermalefliciency of 55% to yield a gas having a'heating value of 268 B. t. u.per cubic foot. At an oxygen-concentration of 71%, 95% of the coal wasgasified with a thermal ei'hciency of to yield a gas having a heatingvalue of 293 B. t. u. per cubic foot.

A rather significant fact is that the rate of nominal heat release wasfound to range around 500,000 B. t. u. per hour per cubic foot of theabove-described apparatus at atmospheric pressure and a gas residencetime of 0.3 second. This rate of heat release is as good or better thanthat secured in conventional carburetted water gas practice. I

Many details of composition, procedure and structure may be variedwithin a wide range without departing fromthe principles of thisinvention, and it is, therefore, not our purpose to limit the patentgranted on this invention otherwise than necessitated by a scope of theappended claims.

We claim: I

1. A continuous method of gasifying coal at a high throughput rate whichcomprises suspending granular coal in a stream of flowing gas, passingsaid suspension-through a restriction to produce an instantaneouspressure drop of at least 15 pounds per square inch to shatter-the coalparticles, immediately confining'said suspension of shattered particlesin a cylindrical, axiallylimited space and incorporating therewithadditional gas capable of reacting with the coal while forming saidsuspension into a vortex to-completely intermix the reactants andfurthercomminute said particles so that at least willpass a' 'mesh screen andat least 50% will passa' 200 mesh screen, axiallydischarging'continuously the comminuted particles from the center ofsaid vortex into a reaction chamber, incorporating with. said dischargedsuspension free oxygen-containing gas in an temperature of saiddischarged suspension a ber at at least 2200 ariiount 'siifiicint toprovide from 0.5 to 1.0 pound of ttit'alffe oxygen per pound of coal togasify the coal particles with theforrnatio'n of ash, maintaining thetemperature of said reaction chamber above the sla'gging the ash andseparating the gas from the slag. V

i 2. A continuous method of gasifying coal at a high throughput ratewhich comprises suspending granular coal in a stream' of compressed gas,passing said suspensi'on through a restriction to produce aninstantaneous pressure drop of at least 15 pounds per square inch toshatter the coal particles, immediately confining said suspension ofshattered particles in a cylindrical, axiallylimited space maintained atelevated temperature and incorporating therewith o'xygen c'ontaining gaswhile forming said suspension into a vortex to completely intermix thereactants and further comminute said particles so that all will passthrough a 100 mesh screen and atleast 50% through a 325 mesh screen,axially discharging continuously the cornminuted particles from thecenter of said vortex into a reaction chamber, incorporating with saiddischarged suspension additional oxygen-cone taining gas in an amountsufiicient to provide 0.6 to 0.9 pound of total free oxygen per pound ofcoal to gasify the coal particles with the formation of ash, saidoxygen-containing gas having at least 60% free oxygen, maintaining thetemperature of said reaction chamber above the slagging temperature ofthe ash, and separating the gas from the slag.

3. A continuous method of gasifying coal at a high throughput rate coalin a stream of compressed gas, passing said suspension through arestriction to produce an instantaneous pressure drop of at least 15pounds per square inch to shatter the c'oal'particles, immediatelyconfining said suspension of shattered particle'sin a cylindrical,axiallylimited space and incorporating therewith one-half to one poundof superheated steam per pound of coal while forming said suspensioninto a vortex to partially d'e volatilize and further comminute saidparticles so that all will pass. through a 100' mesh through a 325 me itscreen, axially discharging continuously the comminuted particles fromthe center of said vortex into areaction' chamber, incorporating withfree oxygen-containing gas in' an amount suflicient to provide from 0.5to 1 pound of total free oxygen'per pound of coal to bring aboutcomplete gasification of the coal with the formation of ash, maintainingthev temperature in said reaction cham- F. to bring'about the blue gasre action and to slag the ash, and discharging said gas from saidreactor after a residence time therein of from 012 to 3.5 seconds.

4; A continuous coal in a stream of compressed gas, passing said suspension through a' restriction to produce an instantaneous pressure drop orat'least 15 pounds per square inc'h'to shatter the coal. particles,introducing the flowing suspension of shattered particles into a streamof superheated steam: confined within a cylindrical axially totalfreeoxygen perpound' of coal to about com plete gasification' of theco'al'with the formation of ash; maintaining the temperature'in saidreaction chamber at at least 2200 F. to bring about the bluegas'reaction" and to slag: the ash; and discharging said gas from said'which comprises suspending granular screen and at least 50% i "ethod ofgasifying' coal at a throughput rate which comprises suspendinggranular" incorporating with said discharged suspension afree oxygencontaining gas" e 1 an amount sufficient to providefrom 0.5 to 1pound-of 9 reactor after a residence time therein of from 0.2 to 3.5seconds.

5. The method of claim 1 in which said reaction chamber is maintained atsuperatmospheric pressure.

6. The method of claim 3 in which said reaction chamber is maintained atsuperatmospheric pressure.

References Cited in the file of this patent UNITED STATES PATENTS885,766 DeLaval Apr. 28, 1908 10 Marconnet Dec. 8, 1908 McDonald Aug. 8,1939 McDonald June 18, 1940 Totzek Feb. 16, 1943 Ramseyer et a1. Aug. 3,1948 Gaucher July 3, 1951 Krejci July 29, 1952

1. A CONTINUOUS METHOD OF GASIFYING COAL AT A HIGH THROUGHPUT RATE WHICHCOMPRISES SUSPENDING A GRANULAR COAL IN A STREAM OF FLOWING GAS, PASSINGSAID SUSPENSION THROUGH A RESTRICTION TO PRODUCE AN INSTNATANEOUSPRESSURE DROP OF AT LEAST 15 POUNDS PER SQUARE INCH TO SHATTER THE COALPARTICLES, IMMEDIATELY CONFINING SAID SUSPENSION OF SHATTERED PARTICLESIN A CYLINDRICAL, AXIALLYLIMITED SPACE AND INCORPORATING THEREWITHADDITIONAL GAS CAPABLE OF REACTING WITH THE COAL WHILE FORMING SAIDSUSPENSION INTO A VORTEX TO COMPLETELY INTERMIX THE REACTANTS ANDFURTHER COMMUNITE SAID PARTICLES SO THAT AT LEAST 80% WILL PASS A 100MESH SCREEN AND AT LEAST 50% WILL PASS 200 MESH SCREEN, AXIALLYDISCHARGING CONTINUOUSLY THE COMMINUTED PARTICLES FROM THE CENTER OFSAID VORTEX INTO A REACTION CHAMBER, INCORPORATING WITH SAID DISCHARGEDSUSPENSION FREE OXYGEN-CONTAINING GAS IN AN AMOUNT SUFFICIENT TO PROVIDEFROM 0.5 TO 1.0 POUND OF TOTAL FREE OXYGEN PER POUND OF COAL TO GASIFYTHE COAL PARTICLES WITH THE FORMATION OF ASH, MAINTAINING THETEMPERATURE OF SAID REACTION CHAMBER ABOVE THE SLAGGING TEMPERATURE OFTHE ASH AND SEPARATING THE GAS FROM THE SLAG.